This study will determine the effects of a deficiency and excess of zinc and an excess of vitamin A on development of esophageal tumors in rats given methylbenzyl nitrosamine. Since alcohol consumption is associated with cancer of the esophagus in U.S. males this factor will also be examined. Preliminary studies have shown a derangement in tissue concentration of zinc and other trace elements and a significantly shorter lag period in tumor development suggesting a potential risk in marginal zinc deficiency. An excess of zinc will be given rats to determine effects on tumor inhibition. Two zinc dependent enzymes will be determined. Tissue distribution of labeled nitrosamine will be evaluated in deficient and control animals.